Electric protection system.



W. M. SCOTT. ELECTRIC PROTECTION SYSTEM. APPLICATION FILED PEB.28, 1914.

1,1 18,064, Patefited Nov. 24, 19 4.

.' v VENTOR '4 ATTORNEY THE NORRIS PETERS 60.. PHDTO-LITHQ, WASHINGTON,1.. v

WILLIAM M. SCOTT, OF RADNOR, PENNSYLVANIA.

ELECTRIC PROTECTION SYSTEM.

Continuation of application Serial No. 685,971, filed March 25, 1912.

Serial No. 821,652.

To all whom it may concern:

Be it known that I, WILLIAM M. Soon, a citizen of the United States,residing in Radnor, in the county of Delaware and State of Pennsylvania,have invented a new and useful Electric Protection System, of which thefollowing is a specification.

My invention relates to an electric protective system, and moreparticularly to a system for the protection of a generator running inparallel with another generator or generators. 1,

My invention resides in the combination with such a generator of acircuit breaker having a plurality of poles, including main andequalizer poles, together with a series tripping coil traversed by thetrue armature current as distinguished from the cur rent that may flowin the main conductor leading to the distribution net-work. And

more particularly my invention resides in the combination with athree-wire generator of a circuit breaker having main and equalizerpoles and a series tripping coil so disposed that it shall be traversedby the true armature current as distinguished from the current in themain leading to the distribution net-work.

My invention resides in the features hereinafter described and claimed.

For an illustration of my invention reference is to be had to theaccompanying drawing, in Which:

Figure 1 is a diagram of circuits, switches, etc, employed to protect athree wire generator. Fig. 2 is a similar diagrammatic view illustratingthe application of my invention to a two-wire generator;

In Fig. 1, at A is indicated the armature of a 'three-wire generatordelivering current at 250 volts, for example, between the outsideconductors 5 and 6, and one-half that voltage between neutral conductor7 and either outside conductor 5 or 6. The armature A is provided, inaddition to the commutator upon which bear the positive and negativebrushes Bp and Ba, respectively, with the four slip rings 8, 10, 12 and14 upon which bear respectively the brushes 9, 11, 13 and 15. The sliprings 8 and 12 are connected to such points in the armature winding thatthere is delivered through them to the brushes 9 and 13 an alternatingcurrent which is passed through the choke coil or inductance 17; and theslip Specification of Letters Patent.

Patented Nov. 24, 1914.

This application filed February 28,

rings 10 and 14 are connected to such points in the armature windingthat there is delivered through them and the brushes 11, 15 analternating current which is passed through the choke coil or inductance16. The alternating currents passing through inductances 16 and 17 aredisplaced in phase by 90. At points 18 and 19 connections are made tothe inductances or balance coils 16 and 17 respectively, these points 18and 19 being at the same potential and constitute a neutral point, athalf voltage, between brushes Bp and Ba. Accordingly the neutralconductor 7 is connected to the balance coils 16 and 17 at 18 and 19.Other types of three wire generator are known to which my invention isapplicable.

The shunt field winding of the generator is omitted for the sake ofclearness. In this type of generator the series field winding is dividedinto halves, one-half for the positive side of the generator andone-half for the negative side of the generator, these series fieldwindings being indicated respectively at Sp and Sn.

The negative brush Bn of the generator is connected through conductor 1and overload tripping coil 47 with one terminal 32 of the negativeequalizer breaker En. One terminal of the negative series field windingis connected to this same terminal 32 through conductor 3, and the otherterminal of the series field winding is connected through conductor 5with one terminal 36 of the ne 'ative main breaker Ma. The positivebrush Bp is connected through conductor 2 and through the current coils44 and 45 with one terminal 24 of the positive equalizer breaker Ep. Oneterminal of the positive series field is connected with this terminal 24through conductor 4, and the other terminal of the winding is connectedthrough conductor 6 with one terminal 20 of the positive main breakerMp. The neu tral conductor 7 is connected through overload tripping coil46 with the terminal 28 of the neutral breaker N.

The movable contact member 21 of the positive main breaker Mp bridgescontacts 20 and 22, the latter being connected to the positive main bus23. Similarly the movable contact member 37 of the negative main breakerMn bridges terminals 36 and 38, the latter connected to the negativemain bus 39. The movable contact member 25 of the positive equalizerbreaker E79 bridges terminals 24 and 26, the latter connected to thepositive equalizer bus 27. Similarly the movable contact member 33 ofthe negative equalizer breaker En bridges terminals 32 and 24, thelatter connected to the negative equalizer bus 35. The movable contactmember 29 of the neutral breaker N bridges terminals 28 and 30, thelatter connected to the neutral bus 31.

The other generator or generators, running in parallel with the oneillustrated in the drawing, is .or are similarly connected throughsimilar apparatus with the busses 23, 27, 31, 35 and 39. *With busses23, 31, and 39 the conductors leading to the consumption circuits areconnected. The equalizer busses 27 and 35 simply connect the similarequalizer breakers of the generators running 1n parallel.

The movable contact members 21, 25, 29, v

33 and 37 may be mechanically connected together,-but insulated fromeach other, so that they may all open circuit simultaneously or allclose circuit simultaneously. tral and equalizer breakers are providedwith latches for restraining the breakers in closed position. Theselatches, or the latch actuators of these three breakers may bemechanically connected together so that when any one latch is actuated,all are actuated simultaneously, with the result that all five breakersor switches open simultaneously. Or a single latch may restrain all thecontact members, and all the tripping devices control or act upon thatlatch. With either equalizer breaker, or with both, are associatedseries and shunt tripping coils for response to reverse energy flow.Such tripping coils are shown at 42 and 44 associated with the positiveequalizer breaker Ep. The current coil 44 is connected in series withthe overload tripping coil 45 which may also trip the latch of thisbreaker. The shunt or potential coils 42 are connected between thenegative armature conductor 1 and the positive armature conductor 2through the bridging member 25 and the terminal 40. When the breakersopen, the connection between terminal 40 and bridging member 25 isbroken, thereby breaking the circuit through the potential coils 42. Theneutral breaker N is provided with an overload tripping coil 46 and thenegative equalizer breaker En is provided with an overload tripping coil47. The operation of the pare ticular apparatus described is as follows:If the loads on the two sides of the three-wire system becomeunbalanced, current proportional to the unbalancing flows through thetripping coil 46 of the neutral breaker N. WVhen this current attains apredetermined value the magnetic effect of coil 46 is sufiicient to tripthe neutral breaker N, and in consequence all the switches and breakersopen The neusimultaneously. Or upon the occurrence of excessive currentflow through the armature A between the neutral conductor 7 and thepositive side of the circuit the overload coil 45 will be energizedsui'liciently to trip the breakers; and similarly upon excessive currentflow through the armature A between conductor 7 and the negative side ofthe circuit the overload coil 47 will trip all the breakers. Or in thecase when the generator whose armature A is receiving current from thebusses instead of supplying current thereto, that is, in the case 01":reversed energy flow, the coils and 44 co-act to trip all the breakers.And it will be noted that when the main and equalizer poles of thecircuit breaking apparatus are open the series field coil is completelyisolated from the buses and the distribution net-work.

It will be noted that by associating the tripping coils 45 and 47 in therelation inclicated with the equalizer breakerathese coils are traversedby the true armature current upon whose excess the breakers are to betripped; while if these coils were connected in the main leads 6 and 5they would not be traversed by all the current flowing in the armaturbut would. in some cases, be traversed by a current of different value,gener ally smaller, which might be flowing through the series fields dueto their parallel connection with the series fields of the othergenerators running in parallel. And as to the reverse "energy flowtripping coils, associated with either or both equalizer leads, thecurrent coil of each reverse current tripping mechanism is traversed bythe true armature current and not by some current of dilierent value asmight occur it the current coil of the reverse energy flow trippingmechanism were associated with either of the main leads 5 or 6.

The current passing from the generator illustrated through the othergenerator or generators running in. parallel and rlowing throughconductors 5 and 6 is not a correct measure of the current carried bythe armature which must be protected against excessive current'flow.Therefore by connecting the overload coils 45 and 47 between thegenerator brushes and'the positive and negative equalizer conductors,the breakers are caused to respond to the current actually flowing inthe armature on either side of the neutral 7. Whatever the cause of thereversed energy flow into the generator, the largest portion of thereverse current will follow the path of least resistance into thearmature,

and this path of least resistance is through invention, connected in anequalizer lead as 1' or 2 between the armature brush and the equalizerconductor.

It is apparent that according to my invention the connection of eachseries field winding between corresponding main andv equalizer poles ofthe circuit breaker mechanism are so made that the total armaturecurrent passes through each of the two overload coils and 47, regardlessof the man ner and proportion in which that current subsequently dividesbetween main and equalizer leads. This arrangement I regard as of greatimportance in the protection of three-wire generators.

In Fig. 2 the same principle is applied to a two-wire generator adaptedto run in parallel with another generator. Here, as in the case of Fig.1, the positive brush Bp connects by conductor 2 through the seriestripping coil 14: of the reverse current tripping apparatus and theseries overload trip ping coil 45 with the terminal 24 of theequalizerpole of circuit breaker mechanism which may include the equalizer poleE7), the main. positive pole Mp, and the main negative pole Ma. Theequalizer pole comprises the movable contact member 25 adapted to bridgethe contact terminals 24 and 26, with which latter connects theequalizer bus 27. The negative brush Ba of the generator armature Aconnects by conductor 1 with the contact terminal 36 of the negativepole of the breaker, through the series tripping coil 48, it such isdesired. The main negative pole comprises the movable contact member 37bridging the contact terminal 86 and 38 with which latter connects themain negative bus 39. The main positive pole comprises the movablecontact member 21 bridging the contact terminals 20 and 22, with whichlatter connects the main positive bus The series field windingassociated with the generator armature A is shown at Sp and, as in Fig.1, is connected between the contact terminals 20 and 24. The shunt fieldwinding of the generator is omitted as in Fig. 1. The shunt or potentialcoils, 12, 42 of the reverse current tripping mechanism are connected,as in Fig. 1, between conductors 1 and the contact 10 associated withmovable contact member 25.

As in Fig. 1, the series tripping coils 4-4 and are traversed by thetrue armature current as distinguished from the current in the main 2-3.And as in Fig. 1, the current through the armature by way of theequalizer bus may be greater than the current in the main 23 and it isto this true armature current that circuit breaker mechanism responds.

This application is a continuation of my application Serial Number685,971, filed March 25, 1912.

What I claim is:

1. The combination with a three-wire generator, of main and equalizerconductors, positive and negative series field windings connectedbetween main and equalizer conductors, circuit breaker mechanismcomprising main and equalizer poles, and a tripping coil thereforconnected in series between one terminal of the armature of saidgenerator and the junction of a series field winding with an equalizerconductor.

The combination with a three-wire generator, of main and equalizerconductors, positive and negative series field windings, main andequalizer busses, circuit,

breaker mechanism comprising main and equalizer poles adapted to connectsaid main and equalizer conductors with said main and equalizer busses,a series field winding connected between a main conductor and anequalizer conductor, and tripping mecha nism comprising a tripping coilconnected in series between one terminal of the armature of saidgenerator and the junction between said main and equalizer conductors,and a potential tripping coil cooperating with said tripping coil andconnected across a circuit of said generator.

4-. The combination with a three-wire generator, of main and equalizerconductors, main and equalizer busses, circuit breaker mechanismcomprising main and equalizer poles adapted to connect said main andequalizer conductors with said main and equalizer busses, a series fieldwinding connected between a main conductor and equalizer conductor, andtripping mechanism comprising a tripping coil connected in seriesbetween one terminal of the armature of said generator and the junctionbe tween said main and equalizer conductors, and a potential trippingcoil cooperating with said tripping coil and connected across theterminals of said armature.

The combination with a three-wire generator, of positive and negativemain conductors, positive and negative equalizer conductors, positiveand negative main busses, positive and negative equalizer busses,circuit breaker mechanism comprising positive and negative main polesand positive and n ative equalizer poles for connecting said conductorsto said busses, positive and negative series field windings connectedrespecfield winding between each'mai-n conductor and equalizerconductor, tripping coils in serles between the armature terminals andthe Junctions of said seriesfield windings :with' said equalizer poles,and a tripping-coil in series with said neutral. pole.

7. The combination with a-three-wire generator, of'positive and negativemain conductors, positive'and negative equalizer conductors, a neutralconductor, circuit breaker mechanism comprising positive andnegative'main poles,=pos1t1ve and negative equalizer poles and a neutralpole, a seriesfield' windingbet-ween each main and equalizer conductor,tripping'zcoil-s in series between the armature terminals and thejunctions of said series field windings with said equalizer poles, atripping coil in series with the neutral conductor, and a reversecurrent tripping mechanism comprising a seriescoil connected between narmature terminal and the junction of one of said" series field wind.-ings with an equalizer conductor, and a potential winding shunted acrossa circuit of said generator.

8. The combinatlon wlth a generator, of main and equallzer'busses, mainand equallzer conductors connected to the sameterminal of the" armatureof said generator, a genera tor field coil connected between a mainconductor and said armature terminal, circuit breaking mechanism forconnecting said conductors with said busses, and tripping mechanismtherefor comprising electro-magnetic means subjected 'to' the combinedeffects of the currents in said main and equalizer conductors.

9. The combination with a generator, of main and equalizer busses, mainand equalizer conductors connected to the same terminal of the armatureof said generator, a series field winding of said generator connected inseries between said terminal of' said armature and said main conductor,circuit breaking mechanism for connecting said conductors with saidbusses, and tripping'mechanism comprising electro-magnetic meanssubjected to the total current flowing through said terminal of saidarmature and said main and equalizer conductors.

10. The combination with a generator, of main and equalizer busses, mainand equalizer conductors, circuit breaking mechanism for connecting saidconductors with said busses, electro-responsive means controlling saidcircuit breaking mechanism, a series field winding, and connections froma terminal of 'thearmature of said generator through saidelectro-responsive means and said series field winding to said mainconductor and through said electro responsive means to said' equalizerconductor.

11. The combination with a three-wire generator, of positive andnegative main conductors, positive and negative equalizer conductors, a'neutral conductor, circuit breaker mechanism comprising positive andnegative main poles andpositive and negative equalizer poles, a seriesfield winding of said'generator connected between each main conductorand equalizer conductor, and tripping 'coils for said circuit breakermechanism connected in series between the armature terminals of saidgenerator and the junctions of said series field windings with saidequalizer poles, and a tripping coil in series with said neutralconductor.

12. The combination with a three-wire generator, ofpositive and negativemain conductors, positive and negative equalizer conductors, a neutralconductor, circuit breaker mechanism comprising-positive and negativemain'poles and positive and negative equalizer poles, a series fieldwinding between each main conductor and equalizer conductor, trippingcoils for said circuit breaker mechanism in series between thearmature'terminals and the junctions of said series field windings withsaid equalizer poles, a tripping cOil in series with said neutralconductor, and a reverse'current tripping mechanism comprising a seriescoil connected between an armature terminal and the junction of one ofsaid series field windingswith an equalizer conductor, and a potentialwinding shunted across a circuit of said generator.

In testimony whereof I have hereunto atfixed nay-signature in thepresence of two subscribing witnesses.

l/NILLTAM M. SCOTT.

Witnesses CAROLYNE'H. V. HEENAN, M. C. GILLEsrm;

Copies of this patent may be obtained for fivecents each, by addressingthe Commissioner of Patents,

Washington, D. C.

